1. Field of the Invention
The present invention relates to a semiconductor integrated circuit device such as a memory or a signal processing device for use in various electronic appliances, and a method for producing the same.
2. Related Background Art
A doped polysilicon layer has been used as a wiring material for various semiconductor devices, as a gate material for a MOSFET, or as an impurity diffusion source. Such doped polysilicon has contained impurities of a single conductive tape, in consideration of easing the manufacturing process.
However, when polysilicon is used as the gate material of a CMOSFET of conventional structure, the electrodes are of the same conductive type, such as n-polysilicon for both NMOSFET and PMOSFET, and the threshold voltages of the two may not be mutually matched.
Also in the ease of a circuit composed of NPN and PNP transistors, polysilicon of only one conductive type can be used, as the emitter diffusion source, in either transistor.
In addition, polysilicon has been associated with drawbacks giving rise to large chip size and a loss in the level of integration, because of its high resistance, requiring a large cross-sectional area for reducing the resistance of the wiring.